Question

The curved surface area of a cone is $4070c{m}^2$ and its diameter is $70$ cm. What is its slant height (in cm) ?

Answer 1

We know, the curved surface area of a cone $=\pi rl$, where $r$ is the radius of the cone and $l$ is the slant height.

Given, curved surface area of cone $=4070c{m}^2$ and diameter $d=70cm$.

Therefore, Radius $r=\frac{d}{2}=\frac{70}{2}=35$ cm.
Hence, curved surface area of this cone $=\frac{22}{7}\times 35\times l$

$\Rightarrow \frac{22}{7}\times 35\times l=4070$

$\Rightarrow l=\frac{7\times 4070}{22\times 35}$
$\Rightarrow l=37$ cm .